A power semiconductor module used for vehicles such as automobiles, has a power converting circuit which converts direct current power into alternating current power or alternating current power into direct current power. The power converting circuit is equipped with a power semiconductor element having large heat value.
For this reason, a case of the power semiconductor module is usually formed with metal. The case is equipped with accommodating space for accommodating a circuit unit including an electronic component such as a power semiconductor element.
As an example of such a power semiconductor module case, a following method is known: fitting a heat sink formed with a large number of radiating fins to an opening part formed in a metal frame object; and joining a matching part of the heat sink and the peripheral part of the opening part of the metal frame object by friction stir welding (see PTL 1, for example).